As a specific example of use of a radiation-curable composition for a cover coat layer of an information recording layer in an optical recording medium, the present inventors have previously filed an application for a patent relating to an optical recording medium employing a radiation-curable composition comprising silica particles made of a hydrolyzate of an oligomer of an alkoxysilane and e.g. a monomer having a urethane bond such as urethane (meth)acrylate and/or its oligomer (see Patent Document 1).
Further, an optical disc is disclosed, which employs, as a radiation-curable composition, an active energy ray-curable composition containing no inorganic substance such as silica particles and containing an oligomer component which is at least one of urethane (meth)acrylate and epoxy (meth)acrylate, a dioxolanyl group-containing (meth)acrylate, and other ethylenic unsaturated compound (see Patent Document 2).
Further, the present inventors previously filed an application for a patent relating to an optical disc employing a radiation-curable composition having a water absorption of at most 2 wt % (see Patent Document 3).
Furthermore, as an adhesive composition for an optical recording medium (optical disc), technique employing a photo-curing method is disclosed (see Patent Document 4).
Patent Document 1: JP-A-2005-36184
Patent Document 2: JP-A-2003-231725
Patent Document 3: JP-A-2006-161030
Patent Document 4: JP-A-2004-359779